Switching system for selectively ionizing gas tubes by radio frequency energy under control of moveable blocking shield



' 1963 M o. PIEPENBURG 3,071,730

SWITCHING SYSTEM FOR SELECTIVELY IONIZING GAS TUBES BY RADIO FREQUENCYENERGY UNDER CONTROL OF MOVEABLE BLOCKING SHIELD Filed Dec. 9, 1958 2Sheets-Sheet 1 INVENTOR.

MARTIN O. P\EPE.NBURG Jan. 1, 1963 M. o. PIEPENBURG 3,071,730

SWITCHING SYSTEM FOR SELECTIVELY IONIZING GAS TUBES BY RADIO FREQUENCYENERGY UNDER CONTROL OF MOVEABLE BLOCKING SHIELD Filed Dec. 9, 1958 2Sheets-Sheet 2 INVENTOR. MART\N O. PIEPENBURG United States PatentUndre- 3,071,730 Patented Jan. 1, 1963 SWITCHING SYSTEM FOR SELECTIVELYIQNIZ- ING GAS TUBES BY RADIO FREQUENCY EN- ERGY UNDER CDNTROL- FMOVEABLE BLOCKING SHIELD Martin 0. Piepenburg, Palatine, .Ill., assignorto Smith- Corona Marcliant Inc., Syracuse, N.Y., a corporation of NewYork 7 Filed Dec. 9, 1958, Ser. No. 779,206 19 Claims. (Cl. 328-) Thisinvention relates to electronic switching systems utilizing gas tubecircuits and more particularly to circuits utilizing a tube in which thegas is ionized by means of externally applied radio frequency energy forcontrolling the starting and stopping of current conduction through thetube.

In electrically operated typewriters such as are used in keyboard typecommunications equipment that sets up,

generates, and transmits coded or electrical impulse groups where eachimpulse group represents a character or letter, it has become necessaryto provide for use in potentially explosive environments a switchingarrangement which is free of arcing that is usually associated withswitching contacts and which will provide troublefree operation over along period of time to reduce maintenance to a minimum. A two-electrodetube which is filled with an inert gas, such as neon, has long beenknown to be ionizable by radio frequency waves received through the tubeenvelope. Such tubes have been used to detect leakage of high frequencyenergy in hollow pipe waveguide installations and, as shown in US.Patent No. 2,658,142, used in high speed commutators by selectivelyionizing the gas in and rendering conductive the tubes in apredetermined sequence.

A principal object of the present invention is to provide a novelswitching methodand system for use with an electrically operatedtypewriter keyboard.

Another object of the present invention is to provide a method forselectively energizing predetermined ones of a plurality of electroniccircuits without utilizing any component which has make or breakcontacts or sliding brushes. i Still another object of the presentinvention is to provide a novel apparatus for effecting gas' tubeswitching which includes reciprocating, oscillating and/or rotatingvanes that serve as means for intermittently shielding and unshieldingthe gas 'tube from a source of radio frequency energy. Such vanes orshielding members may comprise a conductive material but preferablycomprise a member composed of a conductive surface aflixed to aninsulating member with the conductive surface removed at predeter minedpositions on the member to provide'a radio frequency energy window andthus permit momentary energization of the gas tube while normallykeeping the tube blocked from conduction. 1

Other objects of the present invention will become more fully apparentfrom the claims, and from the description as it proceeds in connectionwith the appended drawings in which:

FIGURE 1 is an isometric view of one embodiment of the invention showingthe gas tubes shielded and in the non-activated position in combinationwith a bar type plate energized with radio frequency energy;

FIGURE 2 is an isometric view showing one of the tube shields of FIGUREI removed to a position whereby the gas tube is unshielded;

FIGURE 3 is a pictorial view, partially broken away showing anotherembodiment of the invention utilizing a sliding vane type shield for usein a multiple tube switching system;

FIGURE 4 is a pictorial view of a further embodiment of the inventionshowing a sliding vane type shield of different form;

FIGURES 5a and 5b are pictorial views of the sliding vane of FIGURE 4shown in alternate reverse positions;

FIGURE 6 is a pictorial view of a further embodiment of the inventionshowing the vane shield as a swinging or oscillating member;

FIGURE 7 shows still a further embodiment of the invention, this timewith a revolving disc type radio frequency interrupter; and

FIGURE 8 illustrates a somewhat different principle of operation capableof being used with radio frequency signals in both the VHF and UHFregions. In this embodiment, the solid dielectric gate acts as an energytransfer member instead of a shielding member.

Referring now to FIGURES l and 2, the invention will be described inconnection with a keyboard type communications equipment, such forexample as an electric typewriter having an actuating arm 10 mounted forpivotal movement about pin 12 through connection to the usual key lever(not shown) which may be made through link 11. Actuating arm it), movingin a clockwise direction, pivots about pin 12 and pulls up on pull wireor rod 14, which is linked to a metallic sleeve 16.

Inside sleeve 16, a small tube 18 filled with neon or other suitable gasthatmay be ionized by radio frequency energy, is suitably mountedrelative to a source of radio frequency energy as will be describedbelow.

Abar or plate 20 is connected to a radio frequency tank circuitincluding capacitor 28 and inductor 30 and connected through capacitor36 to a vacuum tube 32 which may be either a power amplifier or anoscillator. In either event, tube 32 serves as a source of radiofrequency oscillations and in the embodiment illustrated serves as anamplifier having its plate voltage fed through choke coil 34. a Hollow,sleeve 16 is grounded and therefore serves as a shield for the RF energyradiating from plate 20 to prevent ionization of the gas in tube 18.When sleeve 16 is raised, as by means of pull wire 14 and actuating armP a battery, and a load resistor 24. The magnitude of voltage .must berelatively low to prevent ionization of the gas in tube 18 resultingfrom the voltage gradient between the two electrodes inside tube 18. Itis further contemplated that the voltage from source 22 will be pulsedin a conventional manner or otherwise of such small magnitude as toassure de-ionization of the gas once the tube envelope is etfectivelyshielded from radio frequency energy. Indicating instrument 26 may beprovided for observation of current flow, but it is not essential to theoperation of the invention.

In operation, when tube shield 16 is in the position illustrated inFIGURE 1 covering tube 18 and preventing the radiated RF energy fromcausing ionization of the gas therein, tube 18 serves as a highimpedance which prevents any substantial current flow through resistor24 thereby resulting in a zero voltage drop across the terminalsthereof. When shield 16 is raised so that tube 18 is exposed to'the highfrequency energy radiating from plate 20 as illustrated in FIGURE 2, thegas in tube 18 is ionized and it then offers a low resistance path tocurrentflow from battery 22 through load resistor 24 thereby resultingin a current flow and a voltage drop across resistor 24. This voltagedrop is then utilized in network 27 of the keyboard controlledcommunication equipment for generating, setting up and transmittingcoded or electrical impulse groups in a well-known manner.

s3 the present invention, the conventional open contact type switch hasbeen obviated from the equipment.

In the embodiment illustrated in FTGURE 1, a number oftubes'corresponding to the number of keys on the typewriter is providedadjacent one or more bars 20 to be energized with radio frequencyenergy. The selective removal of shields 16 from the various ones oftubes 18 results in the coded information being set up in thecommunication system. When shield 16 is dropped back to surround tube18, the voltage supplied by auxiliary source 22is insufiicient to keepthe gas in tube 18 ionized whereby conduction in the tube abruptlyhalts.

The shielding device for tube 18 may take a large variety of forms andthe method of the present invention may be used for many other purposesas will be apparent through contact with associated parts such as coverplate 62. Abutment member 84 is provided at the other end of vane 60 toreceive one end of lever 36 which is mounted for pivotal movement aboutaxis %8. q I

When lever 36 is in the position illustrated, tube 18 7 is shielded fromthe radio frequency energy on antenna plate 58 by the conductivelamination 76'on vane 60.

ship to be separated from each other by separate shielding 32 throughcapacitor 36 to a,tank circuit including capacitor 28 and inductance 30to radiation plates a and 20b. Plates 20a and 20b consist of a centralbody of dielectric material having opposite surfaces covered withmetallic laminations. The RF energy is connected to be emitted from themetallic lamination only on the side of plates 20a and 2017' which isvisible. The edges of the metallic lamination on the side which radiatesRF energy are partly milled off. The reverse side (not shown) is a solidmetallic layer which is not connected to the tank circuit and henceserves to block any RF energy that may leak through the back side toinadvertently ionize tube 180.

Levers 40a, 40b and 400 are mounted for pivotal movement about the axisof pin 41 and adapted to be actuated in any suitable manner bytypewriter keys (not shown) to permit the corresponding ones of vanes38a, 38b, and 38c toslide in a direction urged by compression springs42, and to. a position where windows 44 will be in alignment with gastubes 18 to thereby permit the radio frequency energy from radiatingplates 20a and 20b to pass through windows 44 to gas tubes 18a, 18b or180. typewriter key has been released, the corresponding vane 38 isdriven back against the tension of spring 42 to be in the position forsubsequent selection.

Separate utilization circuits are connected to each of tubes 18a, 18band 180 to be used in selectively establishing the communication orutilization circuits.

Referring now to FIGURES 4 and 5, a further embodiment of the presentinvention is illustrated wherein gas tube 18 is supported on base 50 ofa suitable insulating material. Clip 52 is provided on a side edge 51 ofbase 50 to secure tube 18 in a fixed position adjacent antenna plate 20.Antenna plate 20 in this embodiment is preferably formed of twoangularly related legs 54 and 58 and is secured to base 50 as byterminal 56 so that leg 58 serves as a radiating member facing tube 18.Terminal 56 is connected to the tank circuit of the radio frequency tube32.

Opposite end walls on base 50 contain rectangular grooves for receivingsliding vane 60, shown also in-FIG- URES 5a and 5b, and cover plate 62serves to retain vane 60 in its slidable positionon base 50. Bracket 64is secured to base 50 and contains a bifurcated section 66 through whichthe small end 68 of vane 60 is slidable.

FIGURES 5a and 5b are perspective views of the same vane 60 shown inreversed positions. Between the main After the 58 and gas tube 18 atwhich time the gas in tube '18.

ionizes and current then passes through the circuit including battery22, gas tube 18, meter 26 and load resistor 24. When the force on lever86 is removed, 'spring90 causes vane 60 to move back to the normalposition which shields tube 18- from the ionizing radio frequencyenergy.

In FIGURE 6, a further embodiment of the present invention is shownwherein tube 18 isseparated from RF radiating plate 20 by vane which ismounted for. oscillating movement about axis 102. The position of vane100 is controlled by rigid link 104. The portion of vane 100 which isbetween tube 18 and radiating plate 20 contains a first solid sectioncomprising conductive mate rial 106 and a radio frequency energy window108 which may be either a cut-outor notched section or alternativefl lya dielectric member. As vane 100 swings to and fro;

there results an intermittent breaking of the radio fre-[ quency energyradiated by plate 20 which reaches tube 18 to thereby intermittentlyenergizetube 18 in such manner as to provide a square wave output acrossthe" terminals of load resistor 24. The repetition. rate of such pulsesdepends upon the frequency of the to-and-fro movement of link 104 andthe width of the pulse may be controlled by varying the size of window108. i

In FIGURE 7 a still further embodiment of the present invention is shownwherein radiating plate 20 is separated from gas tube 18 by a rotatingvane 110. Vane 110 is preferably made from a laminated printed circuitboard or equivalent and has a thin layer of copper laminated to one sideof which a portion has been milled off 20 is intermittently blocked andunblocked from gas tube 18 to serve as a means for producing the voltagepulses. The repetition rate of the pulses is determined by the number ofrevolutions per unit oftime of vane 110 while the width of the pulsesmay be varied by varying. V the relative size of window 112 incomparison to the diameter of the vane which shields tube 18 fromreceiving radio frequency energy.

In FIGURE 8 a modified type of vane is illustrated for insertion betweenradiating plate 20 and gas tube 18. In this embodiment, sufficientlyhigh frequency energy is used whereby solid dielectric vane 114 servesnot as a shielding member, but as a dielectric energy transfer. member.In this embodiment the power supplied to antenna 20 is insufficient tocause ionization of the gas in tube 18 when vane 114 is in itsillustrated position. When vane 114 is moved to the region between plate20 and tube 18, it serves to enhance the energy transfer so that Themetallic. lamination 76 also provides a good grounding surface By thepresent invention there is provided a novel contactless switchingcircuit arrangement which is especially well adapted for use aroundexplosive or inflammable environments and which is free of the usualmaintenance requirements of switching equipment having the usualswitching contacts.

The invention may be embodided in other specific forms without departingfrom the spirit or essential characteristics thereof. 'The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

1. Apparatus for selectively energizing predeterminedones of a pluralityof electronic circuits each containing a cold cathode gaseous glowdischarge tube having a dielectric envelope comprising means forenergizing a plurality of said tubes with an operating potentialinsufficient to maintain ionization of the gas therein; means forcontinuously providing a radio frequency radiating field which istotally independent of said operating potential adjacent the envelope ofsaid plurality of tubes which in combination with said operatingpotential is suflicient to cause ionization of the gas in said tubes;means for normally shielding said tubes from said radio frequency fieldto prevent ionization of the gas in said tubes and for selectivelyunshielding said tubes to effect ionization of gas in unshielded ones ofsaid tubes and energization of electronic circuits associated with theunshielded ones of said tubes.

2. In combination with a gas filled tube envelope having an operatingvoltave applied to electrodes therein, said voltage being insuflicientto cause or maintain ionization of the gas in said tube and a loadresistor connected electrically in series circuit relation with saidelectrodes and across which a voltage drop appears when the gas in saidtube is ionized, a radiating member mounted adjacent said tube envelopeand energized with radio frequency energy of a magnitude sufficient tocause and maintain ionization of the gas in said tube in conjunctionwith application of said operating voltage, and means for optionallyshielding the gas in said tube from said radio frequency energy forselectively controlling the time of occurrence of said voltage dropacross said resistor.

3. The combination as defined in claim 2 wherein said shielding meanscomprises a metallic member connected to ground.

4. The combination as defined in claim 2 wherein said shielding meanscomprises a member composed of a con ducting material affixed to onesurface of an insulating material.

5. The combination as defined in claim 2 wherein said shielding meanscomprises a dielectric member which is moved to a position between saidtube and said radiating member to effect ionization of the gas in saidtube and away from said position to effect de-ionization of the gas insaid tube.

6. The combination as defined in claim 2 wherein said shielding means ismounted for reciprocating movement into a space between said tube andsaid radiating member and further includes mechanically operated meansfor effecting reciprocating movement of said metallic member.

7. The combination as defined in claim 6 wherein said shielding meanscomprises a cylindrical metallic member adapted to be placed in aposition surrounding said tube for shielding the gas in said tube fromradio frequency energy.

8. The combination as defined in claim 6 wherein said shielding meanscomprises an elongated vane mounted for axial movement, said vane havingone portion formed to pass radio frequency energy and another portionformed to shield said tube from said radio frequency energy.

9. The combination as defined in claim 8 wherein said vane is composedof laminations of conducting material on opposite sides of insulatingmaterial.

10. The combination as defined in claim 2 wherein said shielding meanscomprises avane mounted for movement about a pivot axis, said vanehaving a first portion formed to pass radio frequency energy and anotherportion formed to shield said tube from said radio frequency energy, andmeans mounting said vane in a space between said tube and said radiatingmember.

11. The combination as defined in claim 10 wherein said vane is mountedfor rotational movement. 7

12. The combination as defined in claim 10 wherein said vane is mountedfor reciprocating movement.

13. In combination, a plurality of gas filled tube envelopes each havingan operating voltage connected to.

electrodes therein, said voltage being insufficient to cause ionizationof the gas in the tube and load resistors connected electrically inseries with said electrodes and across which a voltage drop appears whenthe gas in an associated oneof said tubes is ionized, radiating meansmounted adjacent said tube envelope and energized with radio frequencyenergy of a magnitude sufficient to cause ionization of the gas in saidtube in conjunction with application of said operating voltage, meansfor normally shielding said tubes from said radiating means, and meansfor optionally rendering ineffective the shielding means for selectedones of said tubes.

l4. The combination as defined in claim 13 wherein said radiating meanscomprises a plate connected electrically to a circuit resonant at thefrequency of said radio frequency energy, said plate rigidly mountedadjacent a plurality of said gas filled tubes and said shielding meansan electrically conducting member connected electrically to ground.

15. Apparatus comprising a base; a gas filled tube mounted on said baseand connected to a circuit energized by a source of voltage andcontaining a load re sister; a radiating member mounted on said baseadjacent said tube and connected to a ource of radio frequency energy;shielding means mounted on said base for optional movement between saidtube and said radiating member; spring means for urging said shieldingmeans to a first position which prevents the gas in said tube frombecoming ionized; and means for moving said shielding means against thebias of said spring to cause ionization of the gas in said tube.

16. Apparatus as defined in claim 15 wherein said shielding meanscomprises a flat vane and further comprising side walls ext nding in anangularly disposed relation to a plane surface on said base, said sidewalls I having slots for receiving said flat vane for axial slidingmovement; bracket means extending from one end of said base; meansmounting said spring means between said bracket means and vane; and saidmeans for moving said shielding means comprising an abutment membermounted to contact an end of said vane at a side of said base oppositesaid one end.

17. In combination with a switching system containing a gastubeselectively ionized through exposure to a fixed source of radiofrequency energy mounted adjacent said tube; a vane-like member composedof laminations of conductive material on opposite sides of a iayer ofinsulation material, and means for mounting said vanelike member formovement in a space between said radio frequency energy source and saidtube, said vane-like member having both metallic laminations removed atone position to provide a radio frequency window.

18. In a circuit for controlling the selective on-off switching of autilization circuit: a source of operating voltage; a gas tube having apair of electrodes which conduct current on when the gas is ionized; aload resistor; circuit means for connecting said voltage source, gas

tube electrodes, and load resistor in series, the magnitude of saidvoltage source being. insufficient to cause or maintain ionization ofthe gas in said tube; means for ionizing the gas in said tube comprisinga source of radio frequency voltage which is totally independent fromsaid source of operating voltage, and. a radiating member positionedadjacent said tube and coupled to said radio frequency source; and meansnormally positioned between said radiating member and tube for shieldingsaid tube from the radio frequency energy and selectively movable out ofsaid position to thereby permit the radio frequency energy to ionize thegas in said tube.

19. Apparatus for translating mechanical displacement into an electricalimpulse comprising: a tube envelope having a filling of an ionizable gasand a pair of electrodes; a source of direct current voltage connectedto the electrodes, the magnitude of said voltage being insufiicient tocause ionization of the gas in or current con duction through said tube;a source of radio frequency 8 energy; a radiating member positionedadjacent said tube envelope and coupled to said radio frequency source,said radio frequency energy being of sufficient magnitude to causeionization of said gas in and current conduction throughsaid tube; andmeans movable into and out of a position between said radiating memberand said tube envelope to selectively control the start and stop ofcurrent conduction through said tube.

References Cited in the file of this patent FOREIGN PATENTS GreatBritain Au fz, 193m

1. APPARATUS FOR SELECTIVELY ENERGIZING PREDETERMINED ONES OF APLURALITY OF ELECTRONIC CIRCUITS EACH CONTAINING A COLD CATHODE GASEOUSGLOW DISCHARGE TUBE HAVING A DIELECTRIC ENVELOPE COMPRISING MEANS FORENERGIZING A PLURALITY OF SAID TUBES WITH AN OPERATING POTENTIALINSUFFICIENT TO MAINTAIN IONIZATION OF THE GAS THEREIN; MEANS FORCONTINUOUSLY PROVIDING A RADIO FREQUENCY RADIATING FIELD WHICH ISTOTALLY INDEPENDENT OF SAID OPERATING POTENTIAL ADJACENT THE ENVELOPE OFSAID PLURALITY OF TUBES WHICH IN COMBINATION WITH SAID OPERATINGPOTENTIAL IS SUFFICIENT TO CAUSE IONIZATION OF THE GAS IN SAID TUBES;MEANS FOR NORMALLY SHIELDING SAID TUBES FROM SAID RADIO FREQUENCY FIELDTO PREVENT IONIZATION OF THE GAS IN SAID TUBES AND FOR SELECTIVELYUNSHIELDING SAID TUBES TO EFFECT IONIZATION OF GAS IN UNSHIELDED ONES OFSAID TUBES AND ENERGIZATION OF ELECTRONIC CIRCUITS ASSOCIATED WITH THEUNSHIELDED ONES OF SAID TUBES.